Pug mill knife



Aug. 13.,y 1957 H. n. STRAIGHT PUG MILL KIFE Filed Feb. 4', 1955 United States Patent VPUG MILLKNIFE HalverxR. Straight, Ade'LIowa, .assignor to Straight Engineering Co., AdelyIowa, a corporation of Iowa Application "February 4,1955, SerialNo. '486,065

2 Claims. (Cl. 259-136) This invention relates to an improved pug mill `knife andmorejparticularly toanimprovement in that type of knife fillustrated'and*described 'in lmy issued Patent No. 2;l"09;077. I'One loutstanding 'feature of said invention was in providing a forwardly extending cutting element carried by the outer end of the forward edge of the radial mixing knife. In actual practice this has proved to be very eiiicient in its mixing action and also in the amount of power required to operate the knife. One of the difficulties encountered was in the fact that as the outer end of the forwardly extending portion of the knife wore away, said forwardly extending por-tion became shorter, greatly reducing the eiciency of the knife.

One of the objects of my invention is to so construct the forwardly extending cutting portion of the knife so that i-t may be worn away diametrically Without shortening said forwardly extending portion, thereby greatly increasing the life of the blade.

I have discovered that as the outer end of the forwardly extending portion of the knife wears away the eiciency of the knife is gradually decreased for the reason that the clay is no longer moved inwardly toward the shaft by the cam like upper surface of the forwardly extending cutting portion, a portion of the clay also being pushed outwardly toward the bottom of the mixing casing causing a wedging action between the outer end of the knife and the bottom of said casing, resulting in increased power required to operate the knives, thereby decreasing the advantage obtained by the inward movement of the clay.

It therefore follows that if shortening of the forwardly extending portion of the cutting portion can be avoided the efficiency of the mixing knife can be retained.

It therefore is one of the objects of my invention to maintain the maximum eiciency of the knife over a longer period of time.

A further object of my invention is to further decrease the up-keep cost of the pug mill operation by providing each of the pug knives with a renewable cutting and lifting portion.

A further object of my invention is to improve the streamline construction of the mixing knife to decrease the drying elect due to the introduction of surplus air.

My invention consists in the construction, arrangement and combination of the various parts of the device, whereby the object contemplated and attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawings, in which:

Fig. 1 is a side elevation of my improved pug mill knife the mounting shaft being shown in transverse section.

Fig. 2 is a sectional plan view taken on the line 2-2 of Fig. 1.

Fig. 3 is a sectional view taken on the line 3--3 of Fig. 1.

Fig. 4 is a detail sectional view taken on the line 4 4 of Fig. 1.

Fig. 5 is a plan view of the detachable cutter element.

ICQ

vReferring toFig. 1 of the drawings, Ihave used the reference numeral 10 to indicate the drive `shaft which is supported horizontally above the casing 11 a slight distance. The body 12 of my 'improved knife is formed preferably of cast Ametal such as iron or steel `having a front portion 13 and a rear portion 14. The rear'edge of the portion 13 being inclined downwardly ,and rearwardly, as viewed in Fig. 1, thelower end of :theinclined portion terminating .inithe Aportion y14, said inclinededge havinga groove 16 (see Fig. 2;) for receiving the front side of a shank 17, vthe'lower end of the shank being mounted in the portion;14. The upper :endzof'ithesshank 17 being detachably mounted :inthe shaft :10 :as :clearly illustrated in Fig. 1.

4The lower end `of the portion x13 zand-the front-end ofthe portion 14 'being1form'edwith a tapered hook like portion v18, the upper `andtrear ends of the portion :18 being .provided with shoulders 1.9 tand 21 respectively. The :portion l18 being adapted tto-.receive and support a detachable cutter element 22 having a top edge 23 and a back edge 24. The element 22 having a V-shaped notch 26 extending inwardly from the edges 23 and 24 for receiving the hook portion 18 with the edges 23 and 24 nearly in contact with the corresponding shoulders 19 and 21. A screw 27 provides means for detachably locking the element 22 to the hook portion 18.

The outer peripheral edges of the members 14 and 22 are formed eccentrically with respect to the center of the shaft 10 as clearly illustrated in Fig. 1. The front edge of the body portion 12 being curved outwardly and rearwardly to the front edge 20 of the element 22 terminating in an outwardly and forwardly extending front curved end portion 28 of the element 22 and iinally in a point portion 29 for a chisel like cutting edge.

One of the sides of the body 13 and the element 22 is formed with curved and beveled major pitch surfaces 31 and 32, the opposite side being provided with a minor pitched surface 33, the lower portion of the surface 32 terminating in a rearwardly and inwardly inclined surface 34 tending to force material inwardly toward the shaft 10 as the knife is rotated in a clockwise direction while at the same time surface 31 tends to force the material outwardly, to compress the material as it leaves the pitch surfaces, this is very desirable for reasons clearly set forth in the above referred to issued patent. Forming the outer or peripherical edge of the knife eccentrically with the center of the shaft 10 the heel or back end of the knife is given clearance with relation to the bottom of the dry pan to eliminate wedging of the material between the outer end of the blade and the dry pan.

One of the advantages of my improved pug mill knife `is to increase its life and the cost of upkeep of the mill, resides in the detachable cutter element which may be easily and quickly renewed by simply removing the locking pin 27 permitting the cutting element 22 to be easily removed and a new one substituted. A further advantage resides in adding to the cutting element 22 more material included in the shaded portion 36 forming theblunt end portion 29, the upper edge of the shaded portion represents substantially the contour of the cutter element as illustrated and described in the said issued patent, after it has been slightly worn. It will readily be seen that a great amount of extra wear is thus provided before the inclined portion 34 is reached, the same amount of wear applied to my original form would wear the inclined portion 34 back to the line A-B resulting in a Very short and stubby inclined portion 34 greatly reducing the lifting and inward movement of the material being pugged and also resulting in a wedging action of the material'being mixed between the outer end of the knife and the mixing casing.

Iclaim:

1. A pug knife comprising a blade having longitudinally spaced inner and outer ends, transversely spaced front and rear sides, and laterally spaced side faces, said blade having a forwardly extended transverse projection formed on the front side thereof adjacent the outer end of the blade, said projection being of a smooth contour and being gradually tapered toward the terminal end thereof, said projection having a portion thereof arranged so as to constitute a forward extension of the outer end of said blade, said projection having the terminal end thereof in the form of a at surface inclined inwardly of said blade, and with said projection having a pair of side surfaces which are sloped inwardly of said blade andterminate adjacent the side faces thereof.

2. A pug knife adapted to be mounted on a shaft, said knife comprising a generally hook shape blade having hook and shank portions, means on said shank portion 20 for mounting the blade on said shaft for rotation therewith, with said hook portion having an outer peripheral surface of a generally convex shape and inclined inwardly relative to an arc generated about said shaft and passing through the terminal end of said hook portion, said blade having inner portions of the side surfaces thereof pitched and having outer portions of said side surfaces in planes extended substantially radially of said shaft, with the juncture of the inner and outer portions of each side surface being curved to substantially follow the contour of the outer surface of said hook portion, and with said hook portion being formed with a substan- 10 tially flat surface extending through the terminal end thereof, with said at surface being in an inclined plane located between a plane extended radially of said shaft through the terminal end of said hook portion and a plane tangent to said junctures and extended through 15 said terminal end.

References Cited in the file of this patent UNITED STATES PATENTS 155,439 Gross Sept. 29,1874 306,903 Dandurand Oct. 2l, 1884 2,109,077 Straight Feb. 22, 1938 

